This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-099874, filed Mar. 31, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to an apparatus and method for generating shape data of analytic surface approximate expression by use of three-dimensional shape data approximated by a combination of a plurality of polygons.
Nowadays, CAD (Computer Aided Design) systems, model generation software systems, computer animation software systems, and the like are used to efficiently design products such as machines, architectures, and the like.
VRML (Virtual Reality Modeling Language), which is a standard for exchanging and using three-dimensional shape information of components via the Internet, has been proposed, and is used in practice. Expression of shape data in VRML is an approximation of a three-dimensional shape of an object using a set of a plurality of polygons (polyhedron), and the shape data is widely distributed.
In a given CAD system, kinematic pairs such as coincidence, coaxial, and the like are defined among features (partial shapes such as a cylindrical surface, plane, and the like) as partial shapes of machine components for the purpose of aiding a complicated machine product design using a computer, the positional relationship among components in an assembly is defined and managed, and various functions such as assembly modeling, mechanism simulation, and interference check are implemented. These functions are essential features of a CAD system, and are very effective in design aid.
However, like as the above CAD system cannot use shape data by polyhedron approximation like in VRML. Hence, compatibility and reusability of shape data such as VRML must be improved.
The present invention has been made in consideration of the above situation, and has as its object to provide an apparatus and method for obtaining shape data of analytic surface approximate expression which can be used in a CAD system having various functions such as assembly modeling, mechanism simulation, interference check, and the like.
According to one aspect of the present invention, there is provided a method of generating three-dimensional shape data in analytic surface expression form by using polygonal shape data in which at least a portion of a shape is approximated by a combination of a plurality of polygons, the method comprising: obtaining a set of polygons from the polygonal shape data, each of the polygons satisfying a predetermined selection criterion; fitting an analytic surface in place of the obtained set of polygons; and repeating the step of fitting by obtaining another set of polygons until a predetermined termination condition is satisfied.
According to another aspect of the present invention, there is provided a method for obtaining three-dimensional shape data in analytic surface expression form by using polygonal shape data in which at least a portion of a shape is approximated by a combination of a plurality of polygons, the method comprising: selecting at least one or more polygons from the polygonal shape data in accordance with a predetermined selection criterion; and calculating an analytic surface to be assigned for the one or more polygons.
According to another aspect of the present invention, there is provided an apparatus for generating three-dimensional shape data of analytic surface expression, the apparatus comprising: a storage configure to store polygonal shape data in which at least a portion of a shape is approximated by a combination of a plurality of polygons; a shape data I/O interface configure to read the polygonal data from the storage; and an analytic surface fitting device coupled to the shape data I/O interface, including: a generation device configured to generate a set of polygons from the polygonal shape data, each of the polygons satisfying a predetermined selection criterion; an analytic surface computation device configured to compute a shape parameter of analytic surface, the analytic surface being fitted in place of the obtained set of polygons; and a fitting process controlling device configured to control a fitting process by activating the generation device and analytic surface computation device based on a predetermined termination condition.
According to still another aspect of the present invention, there is provided an apparatus for generating three-dimensional shape data of analytic surface expression, the apparatus comprising: a storage configured to store polygonal shape data in which at least a portion of a shape is approximated by a combination of a plurality of polygons; a shape data I/O interface configure to read the polygonal data from the storage; and analytic surface fitting means coupled to the shape data I/O interface, including: generation means for generating a set of polygons from the polygonal shape data, each of the polygons satisfying a predetermined selection criterion; computation means for computing a shape parameter of analytic surface, the analytic surface being fitted in place of the obtained set of polygons; and fitting process controlling means for controlling a fitting process by activating the generation means and computation means based on a predetermined termination condition.
According to still another aspect of the present invention, there is provided an apparatus for obtaining three-dimensional shape data in analytic surface expression form by using polygonal shape data in which at least a portion of a shape is approximated by a combination of a plurality of polygons, the apparatus comprising: means for selecting at least one or more polygons from the polygonal shape data in accordance with a predetermined selection criterion; and means for calculating an analytic surface to be assigned for the one or more polygons.
According to still another aspect of the present invention, there is provided an article of manufacture comprising a computer usable medium having computer readable program code means embodied for obtaining three-dimensional shape data in analytic surface expression form by using polygonal shape data in which at least a portion of a shape is approximated by a combination of a plurality of polygons, the computer readable program code means comprising: computer readable program code means for causing a computer to select at least one or more polygons from the polygonal shape data in accordance with a predetermined selection criterion; and computer readable program code means for causing a computer to calculate an analytic surface to be assigned for the one or more polygons.
According to still another aspect of the present invention, there is provided an interference check method for checking the presence/absence of geometric interference between three-dimensional shapes using shape data in which at least a portion of a three-dimensional shape is approximately expressed by a combination of a plurality of polygons, the method comprising: obtaining shape data of analytic surface expression by fitting partial sets of the polygons to analytic surfaces; selecting one of an accuracy-oriented processing method and processing speed-oriented processing method of the interference check; selecting one of the shape data of polygon approximate expression and the shape data of analytic surface expression according to the selected processing method; and executing the interference check using the selected shape data.
According to still another aspect of the present invention, there is provided an interference check apparatus for checking the presence/absence of geometric interference between three-dimensional shapes using shape data in which at least a portion of a three-dimensional shape is approximately expressed by a combination of a plurality of polygons, comprising: an analytic surface fit processing device configured to obtain shape data of analytic surface expression by fitting partial sets of the polygons to analytic surfaces; a storage configured to store the shape data of the three-dimensional shape approximately expressed by polygons, and corresponding shape data of analytic surface expression in association with each other; a computation mode selecting device configured to select one of an accuracy-oriented computation mode and processing speed-oriented computation mode of the interference check; a shape data selecting device configured to select one of the shape data of polygon approximate expression and the shape data of analytic surface expression according to the computation mode selected by the computation mode selecting device; and an interference check device configured to execute the interference check process using the shape data selected by the shape data selecting device.
According to still another aspect of the present invention, there is provided an article of manufacture comprising a computer usable medium having computer readable program code means embodied for checking the presence/absence of geometric interference between three-dimensional shapes using shape data in which at least a portion of a three-dimensional shape is approximately expressed by a combination of a plurality of polygons, the computer readable program code means comprising: computer readable program code means for causing a computer to obtain shape data of analytic surface expression by fitting partial sets of the polygons to analytic surfaces; computer readable program code means for causing a computer to select one of an accuracy-oriented processing method and processing speed-oriented processing method of the interference check; computer readable program code means for causing a computer to select one of the shape data of polygon approximate expression and the shape data of analytic surface expression according to the selected processing method; and computer readable program code means for causing a computer to execute the interference check using the selected shape data.